Piston expander



r Dec. 7, 1948.. D; BUSHBY 2,455,728

PISTON EXPANDER Filed Feb. 25, 1946 2 Sheets-Sheet 1 INVENTDR DAV/o Bus/Br ATTDFNEY Dec. 7, 1948. D. BusHBY PISTON EXPANDER 2 Sheets-Sheet 2Filed Feb. 25, 1946 IN l/EN 117 0/71/10 BUS/{BY E Y ATTORNEY PatentedDec. 7, 1 948 j f 2,455,728 ms'rioN EXRANDER David 'Bushby, Regina,Saskatchewan, Carla-dim; assignorto "Va cuum Air Pressure Companyliaimited, Regina, Saskatchewan; iGamada, .a compzmy ofisaskatohewahn,Gzmadalr l t Thisinventionreietesto a piston expander and'ispamticulairly directed toy-providing a frame for expandingemis'ton=-of the type useti in the cylinder of an-internetconrbustion engine. l3

On'eof the important oiij ects -of this invention is to provide anex-pander fmme f or pistons by means ofwh-iche worn piston skirt can-beexpanded easily; quickly, and accurately to bring ail parts "of thepiston sliirt into any desired tolerance fit with themylinfler'wa'l l. wl

A further importantobject of the invention is toprovide an expanderfrafme for pistons in which the expanding pressure is applied onlyto thep-istonskirt portion or portions necessary to bring allparts of thepiston skirt into a, desired tolerance fit withinthe cylinder wail.-

A stilifurther importantobject of the invention is toprovideen expanderframe =for-expanding piston-s whichmey be easily instailedend quicklyadjusted "either when thepistonisinstalledinon inexpensive tomanufacture antiwhich is' e asi ly installed. i

The piston expander of the present invention comprises, in general, mmmhaving a resilient member, said memberbeingof generaiiyeircular sectionand having alternate outwarcily curved high parts for engagement withthe interior wall of a partof a pistomsk-irtto be expanded andinwardlycurved low parts positioned out of engagement with thepiston skirt;andmeains carried by said frame for expanding the liigh pai ts in enoutward direction.

An understanding of theme-Imelin which the above and other obfiectsofthe invention are at" 'tained may be had from the following descr iption, reference being madeto the accompanying drawings; inwhich: i

Figure 1 is "a. verticalsection of piston having an expander ofthe-present *i nven tion instaIledtherein; l

Figure-2 mm horizontal section taken elongthe lineQ-Z of'Ft'gu-re '11,showing the piston s'kirt es being appreciably smaller in diameterthnnthe cylinder Wall; l i

Figure 3 rise *horizontai section taken along the line 2-2 of Figurezllil'lustratingth'e expander as having been installedsandvthe pistonskirt expanded to the cylinder-wall, lest 1mg one wing memberinunexpaznded position;

Figure is a: horizontal: section of awingity'pe pistontakenmalongrthewline fl-l of Figune 3.; ii- .iustmtingp-une thmstvfeceotrthe piston skirt have a wing type "fifllaiims. (01.399412)?ing:heenwexpended into contact with 'thexcylimtier wall;

Figure; .5 is :a. detail View ofltheaexpanzdrrirame and $5613 :scnew.ass'embly in unexpzundetd position taken along the linefiei oiFl-811L138 t3;

Buszwdectail viiew ofrthelexpamder frame =and.z=set :screw assemblyteileenzt along the line 5-5 rot: Figure :3 iliustraiting the expander:its nexnzmcled position; i

:Figume "71is:valhorizontalzsectionof 1 a wing type pistomshint takenalongx theziine ifilliof EiguneM, :iiiustmting :aziternative arrangementof the expander fzmme ain-t1 LSBtI :assemioly; t v

\IFigIIIZ'B ai isk-a detailwiiew taken alongkth'edme :Baflcof .Fiigune'7 showingthe expander membewin unexpandecitposttion;

Eigtuzewfisiswa. detatlsview taken along the line fi-Bxof figure:Teshowingzthe expander members hiuezrnandedmosition; 1

r 1 Figuzieulifiwi'sa bottom plan View :of "a wingt type piston skirtincorporating ax still further. modifioatibnz or the renparnder frameand :set screw assembly? Eifiureailibis aibottom pian view of aconvenpiiston incorponaiting an alternative form 120i ll expander? frameand set screw assembly; andwfl t i 'm'e 1211s ,arcnoss sectionalelevation LOf :9, conrventional type of pistonrincorporating theexpamder mime :nmfl set; r-screw assembly shown in .FFi-gxune Mgtahenalongtheyiine 12-12 of Figure 11 w vhihe: meference :cha-raotersv referto like parts tihnolighout theysp'ecifloationemi drawings.

\ fflhe miumenail zflindtcates a piston such as may 3106; employed in tthe cylinder $24 of e an internal i oombustion engine. The piston'iisformedwith a :sk-int 21pm headii iaandi egnooves 22-for receivingthetoonuentioneii ,pistonxirrgs; The piston Zllrmay whexof theicone/entionaityipe in which theheedend zskirtmmelformeri-zozfanrintegml construction, and may inconpomterrthevwmg, rib and thrustplate ist-nucture oonet'ituting. the ect: matter of mymendinglzazpnlicaitionisezialito. 5%,996 filed August -1 119%, or may heofytherconvention'al type.

i igures 1,?3, 11,7 and 1!) illustrate. a preferred form of expanderincorporated in a piston'ofthe aving; rib and thrust plate construction.Refeming'to these tigures; thenumerai 30 indicates a tzhnust plate; orthrust faioe; against whichpnesemme mayehe brought; to bear toexpandithe wing zone raven indicated why: thenumemi 3.1, ;i e;, theportion of; the skirt which is brought into desired: tolerance fit withthe cylinder wail; the

non -resiiient rigid rib structure is indicatedvby A preferred form of apiston skirt expander is illustrated in Figures 3 and 4 and comprises aframe formed of a relatively rigid member 34 and a resilient member 33.These members may be formed of material such as spring steel, the member34 being of heavier stock than the member 33. The members 33 and 34 areof generally circular section and are substantially parallel over themajor portion of their length, being adapted to fit snugly between thepin bosses 31 and the piston skirt with sufficient clearance from thepin bosses that they do not come into contact with the wrist pin or theconnecting rod assembly during the movement of the piston in thecylinder. The members are formed with parallel, alternate high and lowpoints 33a, 34a, 33b and 3412 respectively. The ends of the outermostresilient member 33 are turned outwardly and are adapted to fit intoslots 35 formed in the piston skirt to anchor the member 33 in place.The

innermost part 34, or the bridge member, is

formed with upwardly turned ends 36 which fit around the edge of the pinbosses 31. The bridge member is formed with threaded housings 38 adaptedto receive the screws 39 and 40. The member 33 is formed with cup shapedindentations 4| which are aligned with the housings 38 and which areadapted to receive the rounded ends of screws 39. The screws 39 actagainst member 33 adjacent to its ends and serve to expand that part.The screw 40 extends through resilient member 33 and acts against apressure plate 42 which is inserted between the end of the screw and theinner wall of the piston skirt and serves to distribute the pressure tothe parts of the piston skirt to be expanded. After tightening, thescrews may be locked in place such as by inserting a wire or a pinthrough the hole 16.

Figure 2 illustrates a piston skirt as being worn to an extent such thatit is of appreciably less diameter than the cylinder in which it isfitted. The manner in which the piston skirt is expanded by the expanderframe is illustrated in Figures 3 and 4. Figure illustrates the relativepositions of the members 33 and 34 when no pressure is applied to thepart 33 and Figure 6 illustrates the part 33 in expanded position by theaction of the set screws 39, the set screw 40 acting directly againstthe thrust face through the pressure plate 42. After installation of one.or more of the expander frames into the piston,

as illustrated in Figures 1, 3 and 4, the set screws 39 and 40 aretightened, thereby urging the resilient member 33 and thrust faceoutwardly until the piston skirt has been brought into desired tolerancefit with the cylinder wall, Only one such frame may be necessary toexpand a worn piston or, alternatively, more than one, as shown inFigure 3, may be employed depending upon the condition of the piston andthe extent to which it may be necessary to expand it.

The expander illustrated in Figure 7 is similar in construction to theexpander illustrated in Figures 1 through 4, the principal difference:being in the arrangement of parts for expanding the resilient member33.

In this modification, the parts 33 and 34 are formed with at least oneand usually several spaced apart inwardly extending cone shapedindentations which form cone shaped bearing surfaces 60 between whichare mounted the plates 5| and 52. These plates are similar in shape tothe cone shaped bearings and are spaced apart,

frame as illustrated in Figure 9, by tightening the machine screw whichextends through one plate and is threaded into the other.

In this modification, the resilient member 33 is expanded against thepiston skirt by turning machine screws 50, which draws the plates 5| and52 together to spread the members 33 and 34 apart and so urge theresilient member 33 against the piston skirt wing members and thrustfaces.

In this modification, the expander frame is inserted into the piston andanchored in place. One or more frames may be inserted into the pistonskirt, depending on the extent to which the piston is to be expanded,without interference with the reciprocal movement of the piston in thecylinder. This modification is slightly more expensive to manufacturebut has the advantage that it is very easy to insert and adjust withoutdisassembling the piston and actuating parts.

The modification of the invention illustrated in Figure 10 employs aframe of substantially circular section adapted to fit snugly into thepiston skirt and formed with a resilient member 10 which is providedwith alternate high and low parts H and 12 of dome shaped section. Thehigh parts I! are adapted to engage theinterior wall of the piston skirtand the inwardly extending low points 12 are positioned out ofengagement with the piston skirt.

A portion of the frame is formed to provide a substantially circularhousing l3v which, over the width of the frame, forms a cone shapedbearing surface adapted to receive the similarly shaped plates 51 and52. These plates are spaced apart, one at each side of the frame, asillustrated in Figure 8, and may be drawn together, as illustrated inFigure 9, by tightening the machine screw 14 which extends through oneplate, 5|. and is threaded into the other plate 52. In this modificationonly a single expander screw assembly is necessary, and expandingpressure of the frame is applied only to the piston skirt portion orportions necessary to bring all parts of the piston skirt into a desiredtolerance fit within the cylinder wall. The frame is easily insertedinto the piston skirt and is anchored in position such as by projections11 formed in the side of the frame adapted to engage in the piston pinholes 15.

A further modification of the invention is illustrated in Figures 11 and12. In this modification the resilient frame is of a roughly arch shapeformed with downwardly extending sides 8| and 82. The side 8! is formedwith one or more projections 83 adapted to fit into a slot 84 formed inthe piston skirt. The other side 82 of the frame is formed with adrilled and threaded housing adapted to receive the set screw 85. Thisset screw is threaded through the frame to act against a pressure plate86 positioned between the side of the frame and the interior wall of theskirt adjacent thereto. Expanding pressure is applied to the pistonskirt by tightening the set screw 85, the pressure being equally appliedto diametrically opposite portions of the piston skirt.

I have found that the piston skirt expander of the present invention hasmany advantages over the expanders of the prior art. While the expanderis equally useful and effective when employed with a piston which asbeen detached from the engine and from the parts from which it isnormally associated, it has the important advantage that it can beinstalled and employed without removing the piston from the cylinder andwithout interfering with the wrist pin and connecting rod parts, theoperation involving merely the removal of the engine crank case and theinsertion of the expander into the piston.

In addition to the above advantage, the employment of the device is verysimple, merely involving tightening one or more set or machine screws,either by a wrench or a screw driver, to bring the worn parts of apiston skirtinto any desired tolerance fit with the cylinder wall.

In addition to the foregoing advantages, the

, expander is easily and cheaply manufactured,

and when installed it occupies very little space in the piston skirt anddoes not interfere in any Way with the normal reciprocal movement of thepiston in its cylinder or with the wrist pin and connecting rod parts.

It will be understood, of course, that modifications may be made in thepreferred embodiments of the invention described and illustrated hereinwithout departing from the scope of the invention as defined by theappended claims.

What I claim as new and desire to protect by Letters Patent of theUnited States is:

1. A piston expander comprising a frame having a resilient member, saidmember being of gentrally circular section and having alternateoutwardly curved high parts for engagement with the interior wall of apart of a piston skirt to be expanded, and inwardly curved low partspositioned out of engagement with the piston skirt, means for securingsaid frame in a piston skirt, and means carried by said frame forexpanding selected high parts of said resilient member in an outwarddirection.

2. A piston expander comprising a frame having a resilient member ofgenerally circular section and formed with alternate outwardly curveddome-shaped high parts for engagement with the interior wall of a partof a piston skirt to be expanded, and inwardly curveddome-shaped lowparts positioned out of engagement with the piston skirt, means forsecuring said frame in a piston skirt, and means carried by said framefor expanding selected high parts of said resilient member in an outwarddirection.

3. A piston expander comprising a frame having a resilient member ofgenerally circular section and formed with alternate outwardly, curvedhigh parts for engagement with the interior wall of a part of a pistonskirt to be expanded and inwardly curved low points positioned out ofengagement with the piston skirt, at least one housing formed by saidframe, and means carried by said housing for urging said high partsagainst the interior wall of the piston skirt.

4. A piston expander comprising a frame having a resilient member ofgenerally circular section and formed with alternate outwardly curvedhigh parts for engagement with the interior wall of a part of a pistonskirt to be expanded and inwardly curvedlow points positioned out ofengagement with the piston skirt, at least one housing formed by saidframe, cone-shaped plates mounted in each bearing, and means for drawingsaid plates together to urge the high parts of said resilient memberagainst the inner surface of the piston skirt.

5. A piston expander comprising a frame having a relatively rigid memberand a resilient member, said members being of generally circular sectionand concentrically disposed over the major portion of their length withthe resilient member outermost, said resilient member being formed withoutwardly curved high parts for engagement with the interior wall of apart of a piston skirt to be expanded and inwardly curved low partspositioned out of engagement with the piston skirt, means for securingsaid frame in a piston skirt, and means carried by said frame forexpanding the high parts of the resilient member in an outwarddirection.

6. A piston expander comprising a frame having a resilient member ofgenerally circular section, means for anchoring said frame to a pistonskirt, a housing carried by said frame diametrically opposite to saidanchoring means, a pressure plate positioned between said housing andthe piston skirt, and a set screw in said housing for acting againstsaid pressure plate.

DAVID BUSHBY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name, Date 1,543,409 Wiggers et al June 23,1925 1,753,113 Floyd Apr. 1, 1930 1,991,655 Bruegger Feb. 19, 19352,005,373 Johnston June 18, 1935 2,212,148 Bretz -1 Aug. 20, 19-10

